[Closed] Metallurgists - help with aluminium

If it's anodised leave it to soak in a bath of caustic soda solution. Bit of fine grit wet and dry afterwards and it'll come up a treat. But won't be anodised obviously so might need occasional polishing to keep it shiny.

NOTE: I am not a metalurgist

wire wool then T-cut?

What a refreshing change.
A genuine 'ist' as opposed to a wooderist, vanerist, runnerist etc etc 😉

Why polish?
If it is anodised won't polishing take away the coating and just accentuate the surface scratches. Unless you go down into the surface to the depth of the deepest scratch.

the scratches on your alu look far deeper than elbow grease is gonna remove - look at youtube for alloy wheel repair to get some idea on how best to go about it.. will probably involve a power tool of some sort.

I don't think it was anodised, unless it was yellow and has faded badly in UV light. Looks to me like a brushed satin finish followed by lots of atmospheric dirt including tars, maybe from smokers? If you want a perfect finish, as above, polish in progressively finer grades of wet 'n dry finishing up with abrasive paste polishes, through Solvol Autosol to car polish, which is the finest. Then protect it with a spray lacquer if it's going to be in a damp environment.

Cover it in stickers.

What kind of metal cart ?

Looks like an airline meal cart to me. Is the OP starting a budget airline?

Ha, I'm no Stelios, but yes it's an airline cart. Thanks for the responses so far, brushed satin finish sounds right - I just guessed that it was anodised seeing the difference in matt (original) and glossy (scratched) areas.

So it sounds like I could try the varying grades of Garryson Aluminium Oxide Abrasive Blocks? Same idea as wet and dry?

Will the scratches/worn patches start to look like the brushed satin areas? Then I guess I could use the Autosol?

Sticker idea is a good shout if my efforts totally ruin it 🙂

Paint...

Wet and dry will get the scratches out easily and quickly. Aluminium is really really soft. The colour change will probably be to oxididisation. I doubt it will be anodized (I'd be surprised). It's an airline cart, they need to be really really cheap and anodizing is expensive.

Can you do a resistance check before and after light polishing with sandpaper? if its anodised then then the resistance will remain the same (unless you go through the anodised) whereas there will be only a slight reduction in resistance if you polish pure aluminium (you will remove the oxide film).

Caustic soda etches Al (attacks it) but will not touch anodise (Al2O3) so don't leave submerged in it over night but dab it or submerge it for minutes at a time. If you remove the surface of the Al with caustic then you might be able to remove the scratches that way

Good luck!

Thanks for all comments, think my next step will be to test the various grades of Garryson abrasive blocks on a section somewhere, and see how it blends the scratches out, and if the resulting finish looks wildly different to the surrounding bits.

Don't want to get caught in the spiral of overdoing a section and having to go over the whole cart frame to match.

Get this part out of the way so I can concentrate on spray painting the panels (thread revival in ten years!) 🙂

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That's definitely treated in some way. Doesn't look like anodising though, maybe electrostatic sprayed? Aerospace parts are highly unlikely to be left in a raw state, even something as basic as a cart.

You may be better with wet & dry paper than abrasive blocks. The blocks will only contact the high spots, so you will eventually get a flat and uniform finish, but it will take much longer than using paper that follows the contours and gets a uniform finish without having to be 100% flat. Whichever, keep all the movement in the same direction.

Try your local bead blasting company they may be able to help.

I'd use it as a tool box.

Looks anodised.
Either way, one of those BBQ cleaning brushes, with the brass bristles, should at least give you a uniform finish. Then a course scotchbrite pad to smooth it out a bit more.
If you get it re-anodised they would etch the surface back anyway but it won't be cheap.

I've just remembered that I know a South African guy who re-finishes and restores airline carts and catering equipment at Johannesburg airport. Have emailed him for advice on the finish and the best way to polish it up.

Back soon.

globalti - very kind of you, thank you! Sounds like the perfect person to ask.

soda blast it to a nice texture?

I've saved the two pics above and emailed them. Back soon with suggestions.

It will be Wednesday as South Africans are all out lighting their barbecues now.

Great, thanks for asking him globalti.

Thanks for other suggestions, soda blasting looks fun but I'd rather start by exploring options that take elbow grease and time than buying more kit.

Not looking for a perfect finish, just to equal out the brushed/anodised/electrostatic sprayed/whatever it is areas with the bits that have worn over the years revealing the shiny metal underneath.

If nothing really does the trick, then I'll decide it's an aesthetically pleasing patina that I wanted to keep!

You are on the right track; I'm afraid his reply, just received, doesn't help much:

[i]"From the pictures that you send it looks like the trolley might be anodised.
The trolley can be stripped but is not really necessary to do so if you want to paint it as for the aluminium extrusions to remove the dents and deep scrapes the extrusions would have to be replaced.
Please take note that if the trolleys are used on an aircraft the paint must be approved for aviation?"[/i]